Procedural criteria for the design and construction of a low-cost solar greenhouse

In this paper, the process followed for designing a low-cost botanical solar greenhouse in a river park in northern Italy is described with the aim of highlighting the strategies adopted to optimize it for robustness under peculiar site-specific constraints. The available design options were indeed substantially constrained by practical reasons deriving from the building site, the very tight budget, and the fact that the greenhouse had to be designed and finally self-built by the designers themselves: six student and two architects (the author included) in the short time (eighty hours) of a building workshop. Furthermore, the decision process had the requirement to be rational, due to the choice of basing each major decision step on a majority vote. The greenhouse has proved to be well-constructible. It will be used in the future for evaluating the correspondence between expected performances - as derived on the basis of thermal and lighting simulations - and recorded performances. The paper focuses on the peculiarities of the decision process that has been adopted, mainly derived from the necessity of “carving” the optimization process inside the reduced search space determined by the local constraints, and the choice of incorporating redundancy as desirable feature – a means for obtaining robustness at thermal and construction level. Some of the major constraints playing a role in the decision process, besides low cost, have been: the presence of a “C” shaped uninsulated concrete south-facing wall; the solar obstructions constituted by hills and deciduous trees; the necessity of avoiding construction delays due to the curing of mortars and concrete; the necessity of basing the control of solar shading devices and ventilation on seasonal, manual controls, so as to reduce the necessity of daily operations; and the necessity of adopting construction solutions suitable to forgive the low levels of precision of the builders.